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Add stricter typing for Events generic parameter #23

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merged 2 commits into from
Jan 16, 2022
Merged

Add stricter typing for Events generic parameter #23

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a6be213
Add stricter typing for Events generic parameter
Jan 6, 2022
8063c1a
Use built-in type to derive function parameters
Jan 7, 2022
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14 changes: 7 additions & 7 deletions index.d.ts
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
export type Arguments<T> = [T] extends [(...args: infer U) => any]
? U
: [T] extends [void] ? [] : [T]
type EventMap = {
[key: string]: (...args: any[]) => void
}

/**
* Type-safe event emitter.
Expand All @@ -20,7 +20,7 @@ export type Arguments<T> = [T] extends [(...args: infer U) => any]
*
* myEmitter.emit("error", "x") // <- Will catch this type error
*/
interface TypedEventEmitter<Events> {
interface TypedEventEmitter<Events extends EventMap> {
addListener<E extends keyof Events> (event: E, listener: Events[E]): this
on<E extends keyof Events> (event: E, listener: Events[E]): this
once<E extends keyof Events> (event: E, listener: Events[E]): this
Expand All @@ -31,11 +31,11 @@ interface TypedEventEmitter<Events> {
removeAllListeners<E extends keyof Events> (event?: E): this
removeListener<E extends keyof Events> (event: E, listener: Events[E]): this

emit<E extends keyof Events> (event: E, ...args: Arguments<Events[E]>): boolean
emit<E extends keyof Events> (event: E, ...args: Parameters<Events[E]>): boolean
// The sloppy `eventNames()` return type is to mitigate type incompatibilities - see #5
eventNames (): (keyof Events | string | symbol)[]
rawListeners<E extends keyof Events> (event: E): Function[]
listeners<E extends keyof Events> (event: E): Function[]
rawListeners<E extends keyof Events> (event: E): Events[E][]
listeners<E extends keyof Events> (event: E): Events[E][]
listenerCount<E extends keyof Events> (event: E): number

getMaxListeners (): number
Expand Down